The present invention relates to door frames, and particularly to metal door frames traditionally used in the construction of office buildings.
Conventionally, metal door frames are pre-manufactured and shipped to a building site fully assembled. The door frame is then placed in a rough opening in the wall and the wall must be built up to the door frame. Since the metal door frame includes the trim, which is intended to overlap the wall surface on both sides of the wall in which the frame is mounted, it is difficult to obtain a clean appearance of the wall around the door frame since the wall must be built up to fit the frame.
Various types of split door frames are known in the art and reference is made to the following patents: U.S. Pat. No. 4,791,758; U.S. Pat. No. 6,550,193; U.S. Pat. No. 4,878,325; U.S. Pat. No. 3,420,003; U.S. Pat. No. 2,853,161; U.S. Pat. No. 4,912,879; U.S. Pat. No. 4,813,204; and U.S. Pat. No. 3,906,671. All of these patents deal with multiple part door frames which allow adjustment of the frame to the width of the wall forming the opening. All of these designs are of varying degrees of complexity which, in applicant's opinion, is the reason why none of them have found commercial success. Furthermore, most of these designs require numerous assembly steps which are necessary for mounting the frame to the wall and adjusting the width of the frame. U.S. Pat. No. 4,791,758 discloses an expandable split door frame that has a first part with an outer flange, a biasing member and a lipped cover that forms a channel. The second member has a lipped inner segment that is slidably arranged in the channel. The second member also has an outer flange for mounting against the wall.
U.S. Pat. No. 6,550,193 discloses a split jam for doors and windows, wherein the jam has a support frame and a trim frame. The support frame is attached to the rough opening of the door frame and then the trim frame is attached to the support frame, for example, by screws.
U.S. Pat. No. 4,878,325 discloses a two-piece adjustable metal door frame which utilizes a fairly complex arrangement of screws, slots and brackets which allows the door frame's width to be adjusted.
U.S. Pat. No. 3,420,003 discloses an adjustable door frame made up of three parts which require relatively precisely produced components, such as the teeth, that serve to hold the trim part in place.
U.S. Pat. No. 2,853,161 discloses a door frame that has an adjustable ratchet arrangement that connects the parts of the frame together.
U.S. Pat. No. 4,912,879 teaches a door frame assembly that utilizes a clip to mount the trim part of the frame to the support part of the frame.
U.S. Pat. No. 4,813,204 teaches a door jam assembly having two parts that slide relative to one another wherein both parts of the frame must be separately fixed to the wall structure.
Finally, U.S. Pat. No. 3,906,671 teaches an adjustable door frame with a support part, a trim part that slides behind the door stop of the support part so as to be connected thereto via screws, and a stop member that snaps over the clip in which the screw heads are located.
As previously mentioned, all these designs require a number of assembly steps for mounting the door frame in the wall opening.